1. Technical Field
The present disclosure relates to field emission displays.
2. Description of the Related Art
A field emission display is a device representing an image through cathode luminescence of a phosphor. This is done by colliding electron emitted from the field emitter of a cathode plate against the phosphor of an anode plate, wherein the cathode plate having the field emitter and the anode plate with the phosphor are formed to be opposite to each other and separated by a given distance (for example, 2 mm). Recently, progress has been made in research and developments of the field emission display as a flat display capable of replacing the conventional cathode ray tube (CRT). Electron emission efficiency in the field emitter is variable depending on a device structure, emitter material and a shape of the emitter.
The structure of the field emission display can be mainly classified into a diode type with a cathode (or emitter) and an anode, and a triode type with a cathode, a gate and an anode. Metal, silicon, diamond, diamond-like carbon, carbon nanotube, and the like are usually used as the emitter material. In general, metal and silicon are used for the triode structure, and diamond, carbon nanotubes, etc. used for the diode structure.
The diode field emitter is usually formed from diamond. The diode field emitter has advantages in simplicity of the manufacturing process and high reliability of the electron emission, even though it has disadvantages in controllability of the electron emission and low-voltage driving, compared with the triode field emitter.
FIG. 7 is a perspective view schematically illustrating the construction of a conventional field emission display having a diode field emitter. A cathode plate has cathode electrodes 61 arranged in a belt shape on a lower glass substrate 60 and film-shaped field emitter materials 62 on a portion of there. An anode plate has transparent anode electrodes 64 arranged in a belt shape on an upper glass substrate 65 and phosphors 63 of red (R), green (G) and blue (B) on a portion of there. The cathode plate and the anode plate are vacuum packaged in parallel, while facing each other, by means of using spacers 66 functioning as a supporter. The cathode electrodes 61 of the cathode plate and the transparent anode electrodes 64 of the anode plate are arranged to intersect each other. In the above, an intersecting region is defined as one pixel. In the field emission display shown in FIG. 7, the electric field required for electron emission is given by the voltage difference between the cathode electrodes 61 and the anode electrodes 64. It has been noted that electron emission usually occurs in the field emitter when the electric field is applied to the field emitter material in the value more than 0.1 V/μm.
In particular, in the field emission display having the diode field emitter of FIG. 7, although the voltage for electron emission may be lowered by reducing the distance between the anode plate and the cathode plate, low voltage driving is nearly impossible since the anode electrode plate 64 is used as the acceleration electrode of the electron as well as the signal line of the field emission display. In the field emission display, a high-energy electron over 200 eV is required to emit the phosphor. The higher the electron energy is, the better the luminous efficiency is. Thus, a high-brightness field emission display can be obtained only at the cost of applying a high voltage to the anode electrode.
What is needed, therefore, is a field emission display having high-brightness with a lower voltage.